Battery packs can be used in cordless electrical appliances with chargeable storage cells for skilled workers, professionals and widely used routine use. For example, nickel-cadmium or nickel-metal hybrids battery cells are used as the storage cells, wherein several such cells are combined to form a battery pack. In the discharged state of the battery pack, the cells can be recharged using a charger device. Embodiments are well-known, in which the battery pack is detachably connected to the cordless electrical appliance to assure that the electrical appliance can be used without prolonged downtimes.
The battery pack is detached from the electrical appliance and charged in a charger Meanwhile, a second, charged battery pack can be connected to the cordless electrical appliance for continued usage while the first battery pack is charging. If the second battery pack discharges, the first battery pack, which has been charged in the interim, can again be connected to the cordless electrical appliance and the second battery pack can be charged in the charger device.
U.S. Pat. No. 6,326,101 discloses a chargeable battery pack that can be detachable connected to an electrical tool. A plurality of vertical cells are arranged in a housing. The battery pack is detachably connected to the electrical appliance using a snap-in mechanism that includes pivotable locking tabs relative to the housing.
Along with small devices, electrical appliances for professional use are increasingly becoming available in cordless configurations. The battery packs have a large number of heavy storage cells depending on the electrical voltage (e.g. 12 V or 24 V). The drawback in the conventional system is that the battery pack, especially in 12 V electrical voltage systems and higher, is quite heavy. Handling such large battery packs is awkward. Furthermore, the battery packs are very sensitive to impact, and thus the well-known snap-in mechanism only conditionally meets the demands of a battery pack over its service life. The possibility to construct a compact battery pack is limited since the locking tabs pivotable relative to the housing require a certain space for their functionality.